Method of preparing an alumina supported dehydrogenation catalyst composition



METHUD F PREPARING AN ALUMINA SUP- ]PURTED DEHYDROGENATION CATALYST COMPOSETION Arnold N. Wennerberg, Chicago, Ill., assignor to Standard (iii Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Aug. 21, 1963, Ser. No. 303,676 1 Claim. (Cl. 252-463) This invention relates to a new catalyst composition and more specifically pertains to a metal oxide catalyst for dehydrogenation.

A new catalyst composition has been discovered which is useful for converting hydrocarbons by dehydrogenation to more useful unsaturated compounds, for example, for

converting monoolefins to conjugated dienes, dehydrogenating alkyl hydrocarbon substituted aromatic hydrocarbons having two or more carbon atoms in the alkyl hydrocarbon substituent to vinyl aromatics, convert-ing certain C mono-olefins to benzene and alkyl substituted benzenes through dehydrogenation and cyclization as well as isomerization and other dehydrogenation processes. This new catalyst composition comprises the oxides of three different classes of metals: low melting metals of periodic group II B having an atomic weight of from about 65 to about 113, e.g. zinc or cadmium, an alkaline earth metal and aluminum. The proportion of oxide of each class of three metals can vary over a wide range. For example, from a component weight ratio based on 10 parts of A1 0 as in the range of 0.1 to 5 low melting metal oxide-0.1 to 5 alkaline earth metal oxide-l0 A1 0 The amount of low melting metal as its oxide need not be equal in weight to alkaline earth metal oxide but rather can vary as in the weight ratio range of low melting metal oxide to alkaline earth metal oxide of from 0.5:1 to 3:1. Desirable catalyst compositions of this invention are those in which the alkaline earth metal oxide are oxides of magnesium, calcium or barium. The catalyst compositions containing oxides of calcium or barium are capable of producing substantially the same percent conversions as those containing magnesium oxide but with respect to selectivity the calcium oxide or barium oxide containing catalysts have demonstrated a lower selectivity level with respect to the desired conversion product than the magnesium oxide containing catalysts have demonstrated. Thus, as a class, low melting metal-MgO- A1 0 catalysts are preferred. Of this preferred class of catalysts, those containing oxides of zinc are preferred over those containing oxides of cadmium.

Examples of typical component weight ratios of catalyst compositions representing the combination of oxides of metals of the most preferred catalyst compositions are illustrated in Table I TABLE I.ZnO-MgO-Alz0 COMPONENT WEIGHT RATIO ZnO MgO A1103 0.10 0.10 0.10 0.20 10 0. 0.10 10 0. 2s 0. 20 10 0. 3s 0. 29 1o 0. 39 0.50 10 0. 5s 0. 2s 10 0. 55 0. 55 10 0. s4 0. 30 10 0.85 0. 51 10 v 1. 09 o. 10 1. 25 1. 25 10 2. 0 2. 0 1o 3. 0 3. 0 10 a. 3 3. 3 1o 5. o 5. o 10 As illustrated above and based on the A1 0 content in the most preferred catalyst composition each of ZnO or nited States Patent 0 3,278,453 Patented Oct. ill, 1966 MgO can vary independent of each other in the range of from 0.1 to 5.0 weight parts per 10' parts by weight of A1 0 and the total of ZnO plus MgO' can vary in the range from 0.02 to 10 weight parts per 100 parts by weight of A1 0 Catalyst compositions like the foregoing typical compositions having cadmium oxide in place of the zinc oxide are typical of other prepared catalyst composit-ions.

One advantage possessed by the catalyst composition of this invention is its ability to dehydr-ogenate monoalipha'tic olefins to conjugated diolefins without skeletal rearrangement of the monoor diolefin. Thus isoamylene can be de'hydro-genated to isoprene without substantial production of piperylene. Another advantage possessed by the catalyst composition is its consistent high selectivity to 99% for mono-olefin dehydrogenation to conjugated dienes and for dehydrogenation of ethyl and isopropyl substituted aromatics to vinyl aromatics. Another advantage possessed by the catalyst composition of this invention is its ability to exercise a catalytic effect to achieve conversions substantially approaching the thermodynamic equilibrium for such reversible conversions. The catalyst compositions also possess the advantageous property of functioning with exceptionally high liquid hourly space velocities (volume of liquid per volume of catalyst per hour) with the high selectivity at substantially the thermodynamic equilibrium conversion.

The catalyst composition of this invention accomplishes the foregoing advantages at substantially lower temperatures than those temperatures used with other catalysts. For example, the catalysts of this invention used for the conversion of isoamylene to isoprene will at liquid hourly space velocities of up to 10 or higher of isoamylene feed and at 525 to 590 C. produce iso'prene with 90 to and above selectivity at conversions of 23 to 45% and above. In contrast a chromia-alumina catalyst at 525 C., tolerating a liquid hourly space velocity of isoamylene at this temperature of only about 1 has an 85% selectivity at 18% conversion to i-sop-rene; and a potassium modified Fe-Cu-Mg catalyst requires a temperature of 650 C. with a liquid hourly space velocity of isoamylene of l to 2 to achieve a 50% conversion to isoprene at 71% selectivity.

The greater tolerance of the catalysts of this invention for high liquid hourly space velocities for other hydrocarbon conversion processes is as striking as for the conversion of ethyl and isopropyl substituted aromatics to vinyl substituted aromatics as for the conversion of mono-olefins to dienes. For example, the catalyst of this invention tolerates liquid hourly space velocities of more than 5 times that tolerated by catalysts in prior commercial operations.

While catalysts in prior commercial operations can be used for hydrocarbon conversions such as isoamylenes to isoprene, butanes to butadiene, et-hylbenzene to styrene, cumene to alpha-methyl styrene and p-cymene to alpha, para-dimethyl styrene using steam as a diluent, the catalyst compositions of this invention cannot tolerate steam. However, other diluents such as inert gases, e.g. nitrogen, argon, etc. and vapors of hydrocarbons inert to the feed hydrocarbon and/ or resultant product can be used. The selection of diluent presents no problem, therefore. Inert hydrocarbon diluents of substantial heat capacity can be used to supply heat to the endothermic dehydrogenation hydrocarbon conversions for which the catalysts of this invention find exceptional use.

Another disadvantage of the catalyst compositions of this invention are their inability to dehydrogenate saturated aliphatic hydrocarbons, alkanes, to mono-olefins. However, this disadvantage can be turned to advantage for the alkanes can be used not only as feed diluents but also as heat carriers.

=3 One convenient method for preparing the catalyst compositions of this invention comprises the dispersion-interaction of molten low melting metal in the correct proportions with precalcined mixture of alkaline earth 4% range of 300 to 525 C. starting at the lower temperature and increasing to the higher temperature, thus calcining and oxidizing the zinc metal. A catalyst whose composition is found by analysis to be 2.0 ZnO/l.4 MgO/IO metal and aluminum compounds providing the ratio of A1 0 results.

alkaline earth metal oxide to A1 0 hereinbefore dis- In another mode of operation, CdO-MgO-Al O type closed. The dispersion of molten low melting metal on catalyst compositions of the preferred class can be prealkaline earth metal oxide-A1 0 can be carried out at pared by dispersing molten cadmium (M.P. 320.9 C.) about 320 to 500 C. under a blanket of gas non-reon a composite of MgO-Al O in the proper weight ratio. active with the catalyst components, e.g. argon, nitrogen, Also ZnO-CaO-Al O ZnO-BaO-Al O CdO-CaO-Al- O etc.; producing a catalyst composition precursor believed and CdO-BaO-Al O catalyst compositions of lower selecto be Zn or cadmium on the alkaline earth metal oxidetivity can be obtained by the same technique by substitut- A1 0 Thereafter, this mixture is heated in the presence ing the proper amount of Ca(OH) or CaO or Ba(OH) of oxygen, in the range of l to 10% oxygen by volume, or BaO for Mg(OH) used in the example.

starting with dilute oxygen such as 1 to 5% 0 by vol., In the oxidizing-calcining step of the technique for to prevent the formation of hot ot whi h would repreparing the catalysts of this invention temperatures at suit in th lo of th l melting metal. Other techthe lower end of 300 to 600 C. range are first employed niques for dispersing metals on solids can be used. with the low oxygen-content gas. The temperature of Catalyst compositions of this invention can also be prethe mass of granulated catalyst precursor is permitted to pared by the interaction of the correct proportions of increas to th upper end of the range, i.e. approaching ZnO or CdO with molten alloy of aluminum and alkaline 600 C. at the upper end of the oxidating-calcining step, earth. e.g. 500550 C. as a maximum.

The catalyst composition is prepared in a granular The following results in 'Table II from dehydrogenafo'rm suitable for use in either a fixed bed catalyst system, {ion experiments, feed Pressure 1 illustrate the a moving catalyst system or a fluidized bed catalyst sysuse of the catalyst compositions on this invention wherein tem. As will be readily understood by those skilled iSI liquid hourly Space Velocity for 20 grams in this phase of catalysis, the operation and use of these of catalys VOluIIle- Y feed Pressure is meant t Part various catalyst bed systems, the size of the granular P s 01'. the f nd th m x ure of diluent gas and catalyst composition is selected according to its ultimate hydrocarbon. In Table II initial conversion is the initial use in fixed, moving or fluidized b d y tem- Ho e conversion of the feed hydrocarbon taken from a single the size of the granular particles of catalyst compositions pass of the feed hydrocarbon over the catalyst.

TABLE II Catalyst ratio weight parts Efficiency Experiment N 0. Compound to be Dehydrogenated, LHSV Diluent, molc/ Temp. Hydrocarbon mole hydro- Percent Percent carbon Zno Mgo A1103 Initial Feed Conversion Selectivity Isoamylene, 590 C 1011 N1, 7.1/1.0-.- 2 1.4 10 45.0 90 Isonmylenc, 525 C 10:1 N2, 71/10.... 2 1. 4 10 23. 8 95 Isoamylene, 590 C. 10:1 N 5.0/1.0- 1.09 0.36 10 26.4 96.3 Isoarnylene, 590 C 5:1 N2, 5.0/1.0..." 0.38 0.3 10 30.6 93.8 Isoamylene, 590 C 5:1 N1, 5.0/1.0 1.25 1.25 10 22.0 90. 4 Isoamylcne, 590 0. 5:1 N /10.... 3.3 3. 3 10 33.7 04. 6 Isoamylcne, 590 O 5;1 Ni, 5.0/1.0-.. 5 1.6 10 33.6 04 Ethylbenzene, 600 5; 1 N1, 9.0/1.0 3. 3 3. 3 10 49. s 97 Cumene, 600 C 51 N2, 9.0/1.0 3. 3 a. 3 10 57. 4 90 Diisobutylene to p-xylene, 600 C 5:1 N2, 7.1/1 0 3. 3 3. 3 10 48 93 Isoarnylene, 525 C 10:1 A6z1 1. 25 1 1. 25 10 22. 4 86 Isoamylene, 525 C 10:1 A7.5:1 2 1 I 10 14.1 Above 85 1 BaO in place of MgO (1.25 Zno-1.25 Bs0-10A1 os). 2 odo in place of Zno (1 CdO-l MgO-IO A1103).

of this invention is not critical to the dehydrogenation When calcium oxide or barium oxide replace magnesireactions and thus size of the granular particles is not um oxide in the catalysts whose uses are hereinbefore a limitation on the novel catalyst compositions but rather illustrated in Table II, the initial selectivities are about 50 size is a subject only to the choice of type of catalyst 55 percent lower. Initial selctivities are calculated from bed in which the novel catalyst compositions are used. conversion and product distribution data after the catalyst The following example illustrates one mode of preparahas been first contacted with hydrocarbon feed for five tion of catalyst compositions of this invention, in this i es n er the conversion conditions. As will be apa composition of the most preferred class of catalyst compredated, the conver $1011 decreases as The catalyst position, comes deactivated by coke deposits and other reactive E a l cite deactivation. For example, the conversion of cumene to alpha-methylstyrene in 2.0 hours on stream decreased A catalyst composition is prepared by suspendmg 20 f 57 to grams M 2 and lqo'grams gamma alumlna (2 The catalyst of this invention can be reactivated or remefsh) F hter 1 dlstlned Water- The Suspenslon generated by treating the deactivated catalyst at 300 to agitated While Water 15 remPved at 20 and 525 C. with air or preferably a mixture of 3 to 10% C. The resulting free flowing granular solid is calcined oxygen and to carbon dioxide 100 to 600 (maxlmum) h- 3 topmduce The catalyst of this invention can also be employed 2 i Y P gran-1113f 9011(1- T1115 P 15 Transto isomerize and dehydrogenate diisobutylene and then erre u-nderdry argon gas blanket to a reaction vessel and 70 cyclize the dehydrogenation product to a xylene product the solid is mixed at 480 C. with 16 grams zinc (M.P. Containing predominantly p xylene 419 i argon g blanket and P under From the foregoing versatility and wide application of argon gas b anket, 20 gfahls 0f the resllhll'lg solid 18 the catalyst composition of this invention, it is readily ferred to a reactor tube in the presence of a gas stream apparent that the catalysts of this invention are exceptionof 97% CO and 3% 0 by volume over the temperature 7 ally useful.

What is claimed is:

A method for the preparation of catalyst compositions comprising alumina and one oxide of each of two classes of metals comprising alkaline earth metals and low melting metals of periodic group IIb which comprises preparing a uniform aqueous dispersion of an alkaline earth metal hydroxide and alumina, removing water from the aqueous dispersion to provide a uniform particle composition of alkaline earth metal hydroxide deposited on alumina, calcining said alkaline earth metal hydroxide on alumina at a temperature in the range of 100 to 600 C. to a free flowing, hygroscopic mixture, blanketing said free flowing, hygroscopic mixture under a gas non-reactive with said free flowing hygroscopic mixture and while under said gas blanket mixing with a low melting metal of periodic group IIb of an atomic weight of from 65 to about 113 at a temperature in the range of form 320 to 500 C., and thereafter heating said mixture in the presence of dilute oxygen in the range of 1 to 10% oxy- References Cited by the Examiner UNITED STATES PATENTS 2,193,464 3/1940 Natta .m 252-475 2,693,497 10/1954 Ballard et al. 25'246'3 X 2,767,221 10/1956 Ballard et a1 25246 3 X 2,822,336 2/1958 Polack 252475 X OSCAR R. VERTIZ, Primary Examiner.

MAURICE A. BRINDISI, Examiner.

G. O-ZAKI, Assistant Examiner. 

